multimeter & 're-soldering advice

I have two disconnected red wires on the left side cups that need reconnecting to the, -L & 3V on the board which you can see on the image below.

My question as a multi-meter novice, how do I test to know which red wire goes to which point?

Also is there any danger of overheating the board on so small solder points?

I got this answer from another forum ,

"Turn on the power and test each wire with the meter. Find a ground point for the black test lead and the touch the red test lead to one of the wires. The one that has 3V on it goes to the 3V and the other goes to the L for the speaker."

but I needed clarification so I asked this question, on the multimeter what setting should I select, "continuous, DC or what?

Also on the ground point, I see a hole with a label "CGND" on the board, I take this as common ground to stick the black probe too?

Any help much appreciated

Wow, its not easy on a android tablet to get images uploaded, anyway its up now so thanks.

Now where do I stick the black probes please on this image?

Wow, its not easy on a android tablet to get images uploaded, anyway its up now so thanks.

Now where do I stick the black probes please on this image?